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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 18: Poster: Polymer Dynamics

CPP 18.23: Poster

Dienstag, 12. März 2013, 18:15–20:15, Poster C

Dynamic consequences of missing chain ends — •Sebastian Gooßen, Ana Rita Brás, Wim Pyckhout-Hintzen, Andreas Wischnewski, Margarita Krutyeva, Jürgen Allgaier, and Dieter Richter — Jülich Centre for Neutron Science, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

The dynamics of cyclic polyethylene glycol (PEG) in a melt was studied by neutron spin echo spectroscopy (NSE) and PFG-NMR for three distinct molecular weights. In comparison with their linear analogs the ring polymers showed a significantly faster center of mass diffusion. This turns out to be an explicit violation of the Rouse model for the smallest rings (∼1 Me). Slightly bigger rings (∼3 Me) fulfill the Rouse behavior perfectly taking into account the different mode structure due to the ring architecture, while linear chains are already slowed down due to the onset of entanglements. For even bigger rings (∼5 Me) the Rouse dynamics does not apply anymore. Obviously topological ring-ring-interactions lead to slower dynamics. However, while for linear chains these topological interactions can be described by entanglements, for the rings they are still not fully understood. Further studies dealt with blends of cyclic and linear PEG. Cyclic polymers in a linear matrix are slowed down effectively with increasing chain length of the linear matrix. On the other hand slightly entangled linear chains (∼3 Me) in a matrix of cyclic polymers of the same molecular weight diffuse much faster than in a linear environment. This very first molecular weight dependent case study on the dynamics of ring polymers in the melt is compared to recent simulation work.